ELECTRICAL PROBLEMS 1972 F100
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5th Wheeling
Joined: Oct 2025
Posts: 40
Likes: 4
Installed a new battery and switch today, no change. Still no lights in cab, no fuel pump running and will not turnover. Used a test light on the starter solenoid and it is getting juice on the starter cable side and turns over when jumped, so the solenoid is good.
How does a guy go about checking the 16ga fuseible link? And is there a good place to find a color preferably wiring diagram, not finding much on the web. Sorry about all the questions, but wiring is my biggest down fall
Dan
How does a guy go about checking the 16ga fuseible link? And is there a good place to find a color preferably wiring diagram, not finding much on the web. Sorry about all the questions, but wiring is my biggest down fall
Dan
Fleet Mechanic
Joined: Aug 2007
Posts: 1,818
Likes: 249
From: Piney Woods of East Texas
I use a test light when ever I'm looking for hot wires. A fuse link normally discolors and burns when fail. Will also have a very soft spot where failed.
Here is your best bet for schematics, not color but coded. https://www.fordification.com/tech/schematics_h.htm
Here is your best bet for schematics, not color but coded. https://www.fordification.com/tech/schematics_h.htm
Thread Starter
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5th Wheeling
Joined: Oct 2025
Posts: 40
Likes: 4
The fusible link has been replaced at one time, used a test light just before it was spliced to the main wire and it is hot. Ran a jumper to the fuel pump and it is working. Used a test light to check the yellow wire into the switch, key on or off no juice , also tested the black wire into the fuse box and no power. Pulled the coil wire out of the distributor cap and jumped it to test for spark, key on or off no spark. Pulled light bulb from dome light and it is good.
So if the fusible link powers the cab, could it be bad without showing any discoloration and no swelling? Running out of ideas here need some HELP from someone good with electrical diagnosis
Thanks for all the help
So if the fusible link powers the cab, could it be bad without showing any discoloration and no swelling? Running out of ideas here need some HELP from someone good with electrical diagnosis
Thanks for all the help
Cross-Country
Joined: May 2025
Posts: 70
Likes: 18
From: PNW
hi, i dont know about your 72 but on my 74 a wire goes from the starter solenoid to a link right below it about 10 inches, below the battery as well, and when wire to it was disconnected from the solenoid it killed all the power to my key, fuse box, headlights, everything if i recall. Poke your probe into the wire on both sides of that one and see what you get.
the second to last post on somebody else's 'backup lights' recent post, has a list of a couple of fusible links, and their locations in it, also for earlier year 74s
the second to last post on somebody else's 'backup lights' recent post, has a list of a couple of fusible links, and their locations in it, also for earlier year 74s
Last edited by bullheimer; Oct 23, 2025 at 03:49 PM.
Cargo Master
Joined: Feb 2006
Posts: 3,009
Likes: 250
From: North Pole, Alaska
Get yourself a multimeter with an ohmmeter/continuity tester rather than a test light. Pick one up at the hardware store like Lowes, Home Depot, Ace, etc. You can isolate wire sections and test for continuity (wholeness of wires). You also have a voltmeter which is helpful for checking if you have a full 12v, or if a battery is fully charged (13.5v). Read across that fusible link. If good, you will get close to 0.0 or some resistance of the wire. If it reads infinity such as a reading where you don't touch the leads together, that is bad.
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5th Wheeling
Joined: Oct 2025
Posts: 40
Likes: 4
Bullheimer went through six pages and could not find a post on "backup lights". Could reference the post as I am interested in other fusible links. From studying the wiring diagram the link of the solenoid branches in many directions. Is the whole black fusible wire of the solenoid a fusible link or just the first 10" if it?? Because it could be burnt some where along that wire hidden in the harness under the tape
Laughing Gas
Joined: Apr 2024
Posts: 801
Likes: 255
From: Laramie Wyoming
So hear me out on this.
Could it not be the starter solenoid?
yes you said you jumped it and everything worked but maybe that’s why it worked was because you jumped it?
what if it’s no good or not grounded?to me that makes more sense because if it’s bad or it is not grounded, from my recent experience, it will produce your symptoms.
just my thoughts if we are still on the differential diagnosis.
Could it not be the starter solenoid?
yes you said you jumped it and everything worked but maybe that’s why it worked was because you jumped it?
what if it’s no good or not grounded?to me that makes more sense because if it’s bad or it is not grounded, from my recent experience, it will produce your symptoms.
just my thoughts if we are still on the differential diagnosis.
Fleet Mechanic
Joined: Aug 2007
Posts: 1,818
Likes: 249
From: Piney Woods of East Texas
Have you checked to see if your getting any power to the fuse block? If the main connection on the fuse block is lost ever thing is dead.
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Cross-Country
Joined: May 2025
Posts: 70
Likes: 18
From: PNW
here is a link to page three. if you read thru it there are also links to wiring diagrams, but i guess you cant print them. i have a six foot monitor and i used the enlarge feature to trace anything. it's a bit overwhelming. https://www.ford-trucks.com/forums/1...l#post21683820 props to tbear853
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5th Wheeling
Joined: Oct 2025
Posts: 40
Likes: 4
Bullheimer saw that post but it's a 77 and mine is a 72, apples to oranges. Are they the same??? Phantomtruck68 you get the prize, after removing the electrical tape from the main harness to access the splice, cut off the heat shrink and the butt connector on the harness side the wire just pulled out, bad crimp.
Replaced the fusible link and now all lights work, fuel pump, cab lights, and headlamps and it turns over. But it still won't start and don't have any spark. ?????????
Replaced the fusible link and now all lights work, fuel pump, cab lights, and headlamps and it turns over. But it still won't start and don't have any spark. ?????????
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5th Wheeling
Joined: Oct 2025
Posts: 40
Likes: 4
Spent some time on this thing, cleaned the MSD ground wire to the head as well as battery ground to the engine and that ground to the frame. Checked the rotor and had power to the red wire on the ignition switch and the pink wire to the distributor from the switch. No power to the coil and tested the MSD box per there instructions and no power.
Not good at this electrical but YouTube is your friend. Tested the coil with an ohm meter on the + and - terminals and it read zero. Have a MSD #8202 oil filled coil and they say not to mount them horizontally which is how it is mounted. Had previously replaced it in May of 23, MSD also makes an epoxy filled coil #8222 which can be mounted horizontally which I have ordered from Oreillys and should have today. Will get on it tomorrow and keep ya posted
Not good at this electrical but YouTube is your friend. Tested the coil with an ohm meter on the + and - terminals and it read zero. Have a MSD #8202 oil filled coil and they say not to mount them horizontally which is how it is mounted. Had previously replaced it in May of 23, MSD also makes an epoxy filled coil #8222 which can be mounted horizontally which I have ordered from Oreillys and should have today. Will get on it tomorrow and keep ya posted
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5th Wheeling
Joined: Oct 2025
Posts: 40
Likes: 4
Installed the coil and still no spark. Checked msd and no spark and no power at the coil connections, have power to the ignition switch as well as power from it to coil, power to msd as well as switched 12v to it.
After much diagnostics and power verification, I noticed a burnt electronic smell coming from the msd box. Have one coming from Summit. Will advise
After much diagnostics and power verification, I noticed a burnt electronic smell coming from the msd box. Have one coming from Summit. Will advise
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5th Wheeling
Joined: Oct 2025
Posts: 40
Likes: 4
the MSD box is 30 years old and it smells of burnt electronics. There is no power coming out of the box to the coil. Been told those boxes are good for about 10 / 14 years. Everything else seems to check out even the stator in the distributor.
Mighty strange ??
Mighty strange ??